1. Field of the Invention
The present invention relates to an original-reading apparatus used in copy machines and facsimile etc., and more particularly to an original-reading apparatus capable of reading light conductive originals.
2. Related Background Art
FIG. 1 shows a general construction of an original-reading apparatus used in a conventional copy machine or the like.
In FIG. 1, an original support 201 is made of transparent glass. A retainer 202 is mounted on an original-retaining cover 210. An image-reading CCD 203 is constructed of a plurality of light-receiving elements aligned in a line.
A motor 209 drives a lamp 204 and mirrors 205-207 into movement in a Y direction, perpendicular to the direction (main scan direction) in which the light-receiving elements of CCD 203 are disposed, so as to subscan the original in the Y direction. The reflecting original such as a book placed on the original support 201 is exposed to the light from an original-exposing lamp 204. The light reflected from the original is received by the CCD 203 to form an image of the original thereon. In this manner, the image of original is read in photoelectric way from the original by means of the CCD 203 for each of scan lines. A sensor 212 detects that an optical system formed of the lamp 204 and mirror 205 is at their home positions (HP), with respect to which the optical system performs the subscan over a predetermined distance.
The original-reading apparatus shown in FIG. 1 suffers from the problem that light conductive originals such as a 35 mm film cannot be read. An apparatus shown in FIG. 2 may be considered to solve the problem. Elements 201-209, 211, and 212 are of the same structural elements as in FIG. 1.
A film, which serves as the light conductive original, is loaded in position within a projector 107. The film 104 is exposed to the light from a lamp 105. Then, the light through the film 104 passes through a lens 103, is reflected by a reflecting mirror 101, then passes through a Fresnel lens 102, and is then projected as a projection image 106 onto the original support 201. The projection image 106 is adjusted its focus by means of the lens 103. The lamps 105 and 204 are controlled to turn on and off by a later described CPU.
When reading the image of the film 104, with the lamp 204 turned on and the lamp 105 turned off, the optical system performs the subscan to read the image 106. This procedure is taken if the light conductive originals are 35 mm negative films and reversal films etc. For light conductive originals such as OHP films (overhead projector) of eight by ten inches, A4 size, or a large size negative films of four by five inches, the film 104 is not loaded into the projector 107 but is placed between the Fresnel lens 102 and the original support 201. The similar image-reading procedure is carried out for the film 104 by utilizing, as a backlight, the light provided by the lamp 105 and lens 103 of the projector 107, mirror 101, and Fresnel lens 102.
However, as shown in FIG. 3, the OHP film originals are often mounted on a frame 301 made of, for example, pasteboard. Reading images from such frame-mounted OHP film originals suffers from the following problems.
Since the frame 301 is not light conductive, simultaneously reading both the image and the information 303 written on the frame 301 is not possible; nor is accurate reading of only the film surface 302 on the inside of the frame 301 possible.